Waste outlet minimum height from water level

[Adam1991]

Hi, we’re installing a normal depth kitchen sink (19cm deep) on our new boat.
 

We are worried that the drainage hole may be coming out of the side of the boat too low. Is it ok to have a skin fitting for the drain at around 9” from the water? We’re aware that the standard is usually 10” from the waterline. 
 

thanks, 

Adam

[Tracy D'arth]

Providing the pipework is incapable of falling apart, the depth can be considered from the top of the sink bowl. So solvent welded or screwed together plumbing  -   no push fit wastes.

[Jen-in-Wellies]

What Tracy said. Most narrow boats end up with the sink waste coming out below 10", just from the constraints of kitchen unit height, sink depth and boat draft. If a wave, wash, or boat heeling over causes the outlet to end up below water, disaster doesn't strike till that water overflows the sink basin, so really really bad!

[Adam1991]

Hi Tracy, thanks for your reply. It’s more the drainage I am looking for advice on rather than the connections. We’ll be using jubilee clipped clear hose between sink plug hole and skin fitting. It’s the skin fitting distance from the water we would like some advice on and whether the height of around 9” is too close to the water line? 

 

thanks, 

Adam 

[blackrose]

9" is ok. I've got one at about 8" above the waterline. As long as the pipework is good and it leads upwards to the sink it should be fine. Use a good PU sealant to bed in the skin fitting rather than silicone. CT-1, Stixall, Marineflex, one of the myriad versions of Sikaflex, etc. 

[Adam1991]

Apologies Tracy, I’ve just realised what you mean. My mistake! A bit too early in the morning for me 😂. Thanks so much for the help. That makes a lot more sense. 
 

Adam 

11 minutes ago, Tracy D'arth said:

Providing the pipework is incapable of falling apart, the depth can be considered from the top of the sink bowl. So solvent welded or screwed together plumbing  -   no push fit wastes.

Apologies Tracy, I’ve just realised what you mean. My mistake! A bit too early in the morning for me 😂. Thanks so much for the help. That makes a lot more sense. 

Thanks all, really helpful 👍

[Tracy D'arth]

Your boat safety man or surveyor may not consider hose and clips to be  compliant.

[Adam1991]

Hi Tracy, what would you advise to connect sink drain hole to the skin fitting? 

[Tony Brooks]

31 minutes ago, Adam Mc Gowan said:

Hi, we’re installing a normal depth kitchen sink (19cm deep) on our new boat.
 

We are worried that the drainage hole may be coming out of the side of the boat too low. Is it ok to have a skin fitting for the drain at around 9” from the water? We’re aware that the standard is usually 10” from the waterline. 
 

thanks, 

Adam

 

If you are fitting out to the RCD/RCR then those are the regulations you need to consider, however I am sure Tracy's answer is complaint. As far as the BSS is concerned the heights for PRIVATE boats are advisory so although not considered best practice less than 10" should not result in a BSS failure.

[Tracy D'arth]

2 minutes ago, Adam Mc Gowan said:

Hi Tracy, what would you advise to connect sink drain hole to the skin fitting? 

Solvent welded standard domestic waste fittings.  Use a trap on the sink outlet ( it will save the diamond ring one day )  and an equivalent size skin outlet.  There are adaptors to fit threads on the skin fitting to pipe

[blackrose]

6 minutes ago, Tracy D'arth said:

Your boat safety man or surveyor may not consider hose and clips to be  compliant.

 

Does waste pipework come under the BSS now? No BSS inspector has ever checked mine and I use double stainless jubilee clips with the screw mechanism turned 180 degrees apart from each other.

 

Maybe it does come under the RCD safety inspection, I don't know about that. 

[PaulJ]

If you can have the outlet properly welded in. Bit of a ball ache I admit but skin fittings do wear away/ get knocked off. 

Once fitted does makes the whole job easier because then you can have exactly the right size / type thread to attach too..

 

[blackrose]

I've never used any waste traps. Waste traps prevent smells coming back up into the sink from mains pipework/sewerage system. You don't really need traps on a boat as the pipework isn't connected to the. mains. 

5 minutes ago, PaulJ said:

If you can have the outlet properly welded in. Bit of a ball ache I admit but skin fittings do wear away/ get knocked off. 

 

 

It's more of a theoretical risk, although I'm sure someone here will have seen skin fittings that have been knocked off or worn away. 

 

On the other hand, welded on pipes can rust through. There are advantages and disadvantages to both. I've never had a problem with brass skin fittings. 

[dmr]

22 minutes ago, Tracy D'arth said:

Solvent welded standard domestic waste fittings.  Use a trap on the sink outlet ( it will save the diamond ring one day )  and an equivalent size skin outlet.  There are adaptors to fit threads on the skin fitting to pipe

I thought that hose and double stainless jubilee clips was the preferred way of doing it. Its good enough to keep hot pressurised water inside an engine cooling system. You don't see solvent weld domestic plumbing on an engine 😀

[GUMPY]

24 minutes ago, PaulJ said:

If you can have the outlet properly welded in. Bit of a ball ache I admit but skin fittings do wear away/ get knocked off. 

Once fitted does makes the whole job easier because then you can have exactly the right size / type thread to attach too..

 

Welded ones rust and fail, unless you never use the sink.

[koukouvagia]

If you need to replace a skin fitting which has a back nut, a removable inspection plate makes access a lot easier.

 

[nb Innisfree]

First I used a 3/4" skin fitting and a waste trap, always getting blocked, a right pain. 

Then replaced SF with 1.5" *

Dumped waste trap and used matching tubing straight from sink plughole to SF,  perfect, no more blockages + greasy water didn't dribble down hull side, if wind was blowing up the plug hole we just stuck the plug in. 

 

*Might have been 1.75", can't remember. 

[koukouvagia]

2 hours ago, nb Innisfree said:

First I used a 3/4" skin fitting and a waste trap, always getting blocked, a right pain. 

Then replaced SF with 1.5" *

Dumped waste trap and used matching tubing straight from sink plughole to SF,  perfect, no more blockages + greasy water didn't dribble down hull side, if wind was blowing up the plug hole we just stuck the plug in. 

 

*Might have been 1.75", can't remember. 

 

[David Schweizer]

7 hours ago, Loddon said:

Welded ones rust and fail, unless you never use the sink.

 

Very true- After about thirty years, which is how long mine lasted

[Tracy D'arth]

I use brass non slotted sink waste flanges as skin fittings with a deflector steel triangle welded in front to prevent then getting wiped off. The advantage is that they are 1 1/2" BSP threaded so a 42mm X  1 1/2" female solvent fitting screws straight on.

[Momac]

8 hours ago, Tracy D'arth said:

Your boat safety man or surveyor may not consider hose and clips to be  compliant.

Why?

 

[David Mack]

 

7 hours ago, Loddon said:

Welded ones rust and fail, unless you never use the sink.

This was a bathroom waste pipe on Belfast. Plastic pipe screwed to a short male threaded pipe welded to the hull. In use all appeared well, but when I unscrewed the waste pipe from the bottom of the wash basin the connection at the other end just fell apart.

[GUMPY]

48 minutes ago, David Schweizer said:

 

Very true- After about thirty years, which is how long mine lasted

Well I've not knocked a brass one off in 30 years